Coupling agent copolymers of amine silicates and organofunctional silanes

ABSTRACT

Coupling agent formulations comprising compatible mixtures of an organofunctional silane and an amine silicate and reinforcing fillers treated with such formulations.

United States Patent Yates COUPLING AGENT COPOLYMERS OF AMINE SILICATESAND ORGANOFUNCTIONAL SILANES inventor: Paul C. Yates, Wilmington, Del.

Assignee: E. 1. du Pont de Nemours and Company,

Wilmington, Del.

Filed: Feb. 16, 1970 Appl. No.: 11,772

U.S. Cl ..106/287, 106/308, 117/100, 117/124, 117/126, 161/192, 260/37,260/41 Int. Cl. ..C09k 3/00 Field of Search ..260/448.2 N, 448.2 E;

106/287 B, 308, 287; l17/126 GS, 100 A [451 Mar. 14, 1972 PrimaryExaminer-Theodore Morris Attamey-Lynn N. Fisher [57] ABSTRACT Couplingagent formulations comprising compatible mixtures of an organofunctionalsilane and an amine silicate and reinforcing fillers treated with suchformulations.

5 Claims, No Drawings COUPLING AGENT COPOLYMERS OF AMINE SILICATES ANDORGANOFUNCTIONAL SILANES BACKGROUND OF THE INVENTION organofunctionalsilanes are well known in the laminateforming arts as excellent couplingagents for bonding organic resins to embedded reinforcement materials.Ordinarily, reinforcement materials are coated with and bonded tocoupling agents and then embedded in the impregnating resins which inturn bond with functional groups on the coupling agents. Selection ofthe proper organofunctional silane is usually determined by choosing acoupling agent with a functional group that is capable of undergoing aknown polymerizationcondensation with one or more of the functionalgroups of the impregnating resin. Proper matching of silane organicfunctional groups with those of the impregnating resin is essential tothe formation of strong, water-resistant chemical linkage of the twomaterials. It appears that only a percentage of the total number ofsilane organic functional groups polymerize with the condensablereactive sites of the organic resins. Therefore the spacing offunctional organic groups on the reinforcement material, to more closelycorrespond with the location of the condensable reactive sites on theresins, can substantially reduce the amount of silane needed in a sizeor a finish without any reduction in bonding efficiency and strengths.

I have found that the formulation of the organofunctional silane with anamine silicate enables one to better control the spacial arrangement ofthe coupling agent along the surface of the reinforcement material. Bymanipulation of the spacing of the coupling agent to more closelycorrespond to the coreactive sites on the polymeric resins, comparableor superior bonding is attained, accompanied by a substantial reductionin the amount of silane needed in the size or finish.

SUMMARY OF THE INVENTION In summary, this invention pertains to couplingagent formulations comprising compatible mixtures having 25 to 90percent of the total silicon percent in the form of an organofunctionalsilane of the general formula R is selected from the group consisting ofcarboxyalkenyl, alkyl, aminoalkyl, thioalkyl, and epoxy substitutedalkyl, where the alkyl or alkenyl has one to 18 carbon atoms;

X is selected from the group consisting of hydroxyl, halogen, alkoxyhaving one to six carbon atoms, aryloxy, and amino;

n is a positive integer of from one to three;

and having 10 to 75 percent of the total silica present in the form ofan amine silicate wherein the degree of polymerization of thepolysilicate is less than 1,000 and the amine component is at least oneamine selected from the group consisting of (I) compounds having theformula:

wherein R R and R are independently selected from the group consistingof hydrogen, alkyl having one to six carbon atoms, and alkanol havingone to six carbon atoms, with the proviso that R,, R and R cannot all behydrogen; (II) morpholine, and (Ill) cyclohexylamine, the amine beingpresent in an amount of at least 0.1 mole per mole of silica introducedin the form of the amine silicate. The compositions of this inventionmay also contain a small amount of a strong inorganic or organic basesuch as sodium, potassium or lithium hydroxide, ortetramethylammonium-or guanidine hydroxide, so long as the molar ratioof silica in the composition relative to the molar ratio of M 0, where Mis the cation of the strong base, is greater than six. Some of the aminesilicates are described in greater detail in a patent to Weldes, US.Pat. No. 3,326,910, and others in the applicants copending application,Ser. No. 823,185.

DESCRIPTION OF THE INVENTION This invention is specifically directedtoward coupling agent formulations comprising amine silicates having adegree of polymerization of less than 1,000, and an organofunctionalsilane compound of the formula R,,-SiX and methods for couplingreinforcement materials to organic resins.

The coupling agent formulations of this invention, specifically theamine silicate-organosilane copolymer, can be further formulated withother processing additives such as organic resinous bonding agents,lubricants, emulsifiers, antifoarning agents and antistatic agents forsizing or finishing reinforcement materials. These coupling agentformulations, when present in sizing or finishing solutions, can beapplied to reinforcing materials with no sacrifice of bonding efficiencyor strength.

Coupling Agent Formulation Components The organofunctional silanecompounds which can be used in the coupling agent formulations of thisinvention have the general formula R is selected from the groupconsisting of carboxyalkenyl,

alkyl, aminoalkyl, thioalkyl and epoxy substituted alkyl, where thealkyl or alkenyl have one to 18 carbon atoms;

X is selected from the group consisting of hydroxyl,

halogen, alkoxy having one to six carbon atoms, aryloxy, and amino.

The organofunctional silanes of this invention are multifunctionalcompounds and can be readily hydrolyzed and polymerized with aminesilicates, copolymerized with each other, and copolymerized withorganic, impregnating resins.

The preferred organofunctional silanes have R groups such as acrylate,methacrylate, methacryloxypropyl, gammaaminopropyl, vinyl, alkyl,methallyl, crotyl and stearyl and X groups such as methoxy and ethoxy.

The organofunctional silanes which are most preferred for the couplingagent formulations of this invention aregammamethacryloxypropyl-trimethoxysilane,gamma-aminopropyltriethoxysilane and vinyl triethoxysilane.

The amine silicates which can be used in the coupling agent formulationof this invention have a degree of polymerization of the polysilicate ofless than 1,000 and the amine component is at least one amine selectedfrom the group consisting of (1) compounds having the formula:

wherein R R and R are independently selected from the group consistingof hydrogen, alkyl having one to six carbon atoms, and alkanol havingone to six carbon atoms, with the proviso that R R and R cannot all behydrogen; (ll) morpholine, and (III) cyclohexylamine, the amine beingpresent in an amount of at least 0.1 mole per mole of silica in the formof the amine silicate. The compositions of this invention may alsocontain a small amount of a strong inorganic or organic base such assodium, potassium or lithium hydroxide, or tetramethylammonium orguanidine hydroxide, so long as the molar ratio of silica in thecomposition relative to the molar ratio of M 0, where M is the cation ofthe strong base, is

greater than 6. Some of the amine silicates are described in greaterdetail in a patent to Weldes, US. Pat. No. 3,326,910, and others in theapplicants copending application Ser. No. 823,185.

The degree of polymerization can be measured by techniques known in theart which are sensitive to the molecular weight of polymeric molecules,such as by measurements of the intrinsic viscosity, by light scattering,by measurements of the osmotic pressure, or by measurements of theelevation of the boiling point or depression of the freezing point ofthe solution.

Molecular weight can also be determined by procedures specific tosilica, such as titration with a gelatin, as given in an article by R.K. Her and P. S. Pinkney (Ind. Eng. Chem. 39, 1379 (1947 by measurementof the rate of color development using a molybdic acid colorimetricreagent as disclosed in an article by G. B. Alexander (ThePolymerization of Monosilicic Acid, J. Am. Chem. Soc., 76, 2094 (1954)}.

, The amine silicate should have a degree of polymerization less than1,000 and preferably less than about 100. The most highly preferred areamine silicates having a degree of polymerization less than 10.

The most preferred amine silicates are those of dimethylarnine and ofethanolamine. Also highly preferred are compositions of dimethylamine orethanolamine with small amounts of strong stabilizing bases in additionto the amines. Sodium hydroxide, potassium hydroxide, guanidinehydroxide and tetramethylarnmonium hydroxide in molar ratio proportionsof to l to 30 to l are preferred, where these refer to molar ratio ofsilica to M 0, M being the cation of the strong base.

In the formulation of coupling agent solutions of this invention, theorganofunctional silanes can be hydrolyzed and then mixed with the aminesilicates. Alternatively, the amine silicate constituent itselffunctions as a catalyst for the hydrolysis of the organosilanes', thusmixing the two essential ingredients in aqueous solution causeshydrolysis and polymerization condensation to occur spontaneously.

The copolymerization of the amine silicates with the organosilanesincreases the functionality for condensation reactions in the resultingcopolymers and at the same time increases the variety of spacing offunctional group arrangements possible for the copolymers relative tothose that could be obtained with the organosilanes alone. The largerthe number of exposed functional groups on the amine silicatesilanecopolymers, the greater the probability of copolymerizing with theimpregnating resin. Unfortunately, multifunctional silanes whenproximately polymerized to reinforcement materials causes suchreinforcement materials to become very hydrophobic, thereby resulting inpoor wetting of the materials with impregnating resins.

The copolymerization of the amine silicate with organofunctional silanesprior to sizing or finishing the reinforcing materials, permits the useof these polyfunctional silanes without the concomitant disadvantagesencountered when such groups are proximately bonded to the reinforcingmaterials. In addition, the copolymerization of silane with aminesilicates enables substantial reduction in the total amount oforganofunctional silanes needed to coat the reinforcing materials. Thereduction in concentration of silane does not reduce bonding efi'rciencyor strengths; quite the contrary, the corresponding spacing and improvedwetting in some instances produces superior results.

it is hypothesized that comparable and superior bonding strengths andreduced silane concentrations are probably attributable to a moreefficient matching of organosilane functional groups with thecondensable reactive sites on the resin, or possibly the more numerousand more complex bonding of the coupling agent copolymers to thereinforcement materials.

In summary, the addition of the amine silicates increases the number ofreactive sites which can bond to the reinforcing materials furtherpermits the use of multifunctional silanes, thereby enhancingcopolymerization with the impregnating resins and reduces the totalconcentration of organosilane needed to achieve comparable or superiorbonding strengths. Because of this multiple bonding, both at the site ofreinforcing materials and at the copolymerization sites of the resins,adhesion to the reinforcing materials is substantially increased. Inaddition, water resistance is correspondingly enhanced. Resinouslaminates structurally reinforced with the compositions of thisinvention have dry and wet strengths and modulus of rupture values equalto or greater than resinous laminates where organofunctional silanes areused alone.

Preparation of Coupling Agent Formulations The coupling agentformulations are prepared by mixing the two essential ingredients intheir proper proportions in an appropriate solvent. As previously noted,the organofunctional silane contributes 25 to mole percent of the totalsilicon present in the formulation and the amine silicate comprises 10to 75 mole percent of the total silicon present in the formulation.Generally, mixing of the essential ingredients is performed in diluteaqueous solution. This minimizes the possibility of premature reactionbetween the essential ingredients. The combined concentration of theessential ingredients in the formulation will range from one tenth toten per cent by weight of the formulation, with 0.25 to 2 percent beingpreferred.

Caution must be exercised with certain rather easily hydrolyzed Rgroups, such as gamma-methacryloxypropyl, since the ester linkage inthis R group is susceptible to hydrolysis. The amine silicatecompositions of this invention, being basic in character, will tend topromote this hydrolysis if excessive times are allowed after contactingthe two ingredients prior to applying to the surfaces of the glassfibers and drying down. To avoid the possibility of hydrolyzing thissusceptible ester linkage, the gamma-methacryloxypropyltrimethoxysilaneshould be first hydrolyzed in aqueous solution and this mixed just priorto application with the amine silicate constituent of the invention.

After hydrolysis of the organosilane and mixture with the aminesilicates, the compositions of the invention will have a pH between 8and 11, depending on the concentration. Particularly in the lower pHrange the compositions of the invention will have a tendency toward raidpolymerization and should be applied promptly to the reinforcing fillersto avoid the possibility of gelation. At the upper pH range thesolutions are stable for longer periods of time, ranging up to 12 hoursor more.

Methods of Treating Reinforcing Materials with Coupling AgentFormulations Formulations of hydrolyzed, partially polymerized essentialingredients of this invention can be applied to the reinforcing fillersin any convenient manner. Normally, a reinforcing filler is immersed inthe dilute aqueous solution containing the coupling agent formulation,removed from the treating bath, and excess moisture wrung out. Theproper concentration of coupling agent formulation (essentialingredients) will range from 0.01 to 20 percent by weight by essentialingredients based on the weight of the reinforcing material. Ordinarily0.25 percent to 10 percent weight is preferred. Ordinarily thereinforcing materials having the greatest surface area will containlarger amounts of essential coupling agent formulation components. Lowsurface area materials, such as glass fibers, can be bound to theorganic resins with lower concentrations of coupling agent.

After immersion and removal of excess moisture (solvent) the coatedsupport materials are rapidly dried at temperatures as high as 200 C.provided, however, that the organic portions of the coupling agent donot undergo degradation at these temperatures. This rapid curingcompletes the polymerization of the constituents with one another andthe bonding of the coupling agent to the support material. Althoughdrying can be accomplished at room temperature, curing betweentemperatures of 50 and 180 C. is recommended and preferred. Of course,curing times will vary inversely with the temperature and may range froma few minutes at 200 C. to 24 hours at room temperature.

A more economic and convenient method for applying a coupling agent tosupport materials, is the treatment of these materials with couplingagents as an integral step in their manufacture. In a typical sizingprocess, the various components of the size are premixed and applied tothe reinforcement materials by padding or spraying methods.

Because the size is designed to perform a plurality of functions (forinstance, bond multifilamentous glass fibrils into a coherent strand,protect support materials from self abrasion and chemical degradationduring handling or weaving and couple the support materials to polymericresins), it can contain several components in addition to couplingagents. A typical size for glass fibers can contain organic resinousbonding agents, lubricants, antistatic agents, emulsifiers, and couplingagents.

Reinforcing Materials A reinforcing material is a substance which whenincorporated into or coupled to the organic resin (impregnating resin)enhances the strength and modulus of the cured laminate. Reinforcingmaterials of this invention can be in the form of rovings, fabrics,continuous and chopped-strand mat, chopped strands and milled fiber.Among the more popular of the reinforcing materials are the low sodiumglass fibers (E glass fibers and beta-glass fibers) asbestos, sisal,cotton, quartz, glass microspheres, graphite, refractory aluminasilicate fibers, and metal whiskers.

Low sodium glass fibers are by far the most popular of the reinforcingmaterials, and are preferred for the laminate compositions of thisinvention. Compositions of low sodium glass fibers can, and often do,vary; however, low alkali metal oxide content is essential. Typical lowsodium glass fibers can have the following compositions:

Elements Per Cent ofContent SiO 54.3%

A1 0 and Fe,0, 15.2%

MgO 4.7%

N3 0 and KO 0.6%

It has become rather common practice to incorporate less expensivefiller materials into the laminating composition for reasons of economyand in some instances for reasons of esthetics.

Representative of the filler materials which can be incorporated intothe laminating composition of this invention are kaolin, calciumcarbonate, talc, chrysotile asbestos, alumina, zircon, zirconium,magnesium oxide, colloidal amorphous silica, attapulgite, wollastonite,perlite, fly ash, calcium silicate, aggregate and fibers.

The amount of reinforcing materials present in the composition may be aslittle as 1 percent by weight and as high as 90 percent by weight of thelaminated particle, depending, of course, on the relative densities ofthe resins, the reinforcing materials and the method of fabrication.impregnating Resins The organic resinous materials which copolymerizewith the organofunctional groups of the coupling agent composition areamorphous, organic, semisolid or solid materials produced by union(polymerization or condensation) of a large number of molecules of one,two or less frequently three relatively simple compounds. Resin, as theterm is used in this invention embraces both synthetic and chemicallymodified natural resins. Among the more useful organic resinousmaterials which can be bonded to reinforcement or substrate materialswith the coupling agent formulations of this invention are the saturatedand unsaturated polyester resins, the epoxy resins, the phenolic resins,the melamine resins, the ureaformaldehyde resins, polystyrene,copolymerized styreneacrylonitrile, polypropylene, polyethylene,polyacetal, polycarbonate, copolymerized acrylonitrile-butadienestyrene,polyvinyl chloride, polyurethane, polysulfone, polyphenyl oxide, andfiuoroplastics.

Methods of Bonding Reinforcing Materials to Organic lmpregnating ResinsThe coated support material is cut in the shape of the object to belaminated, placed on the laminate die and covered with sufficientimpregnating resin to wet the support material. Support material orresin are successively layered one atop another until the requisite plylaminate is attained. After layering, excess resin and air bubbles aresqueezed out by rolling the laminate between rubber rollers. Theslightly compressed laminate can then be hot-pressed until the resinsets or melts. After hot-pressing is complete the laminate is cooled andremoved from the die. The resulting laminate will exhibit both excellentwet and dry strengths which will equal or exceed those attained whereundiluted organofunctional silanes are used alone to bond theimpregnating resins to the reinforcing materials.

The following examples are presented to further illustrate, not limit,this invention. Parts and percentages as they are used in the examples,refer to weight unless otherwise stipulated. EXAMPLE 1 The aminesilicate essential ingredient is prepared by weighing 1,500 parts of asodium silicate commercial solution having 30 percent SiO and 8.7percent sodium oxide designated Du Pont F Grade sodium silicate into 300parts of distilled water. This is stirred in a high speed steel stirrer,and 2,725 parts ofa dimethylamine form ofa cation exchange resin isstirred into it for 5 minutes. This resin is a sulfonated polystyrenepolymer having approximately 4 milliequivalents of ion exchange capacityper gram of dry resin and is prepared by reacting the correspondinghydrogen form of the resin with an excess of aqueous dimethylaminesolution, followed by washing. The resin is filtered off and treatmentcontinued with a second portion of 2,725 parts of dimethylamine form ofthe ion exchange resin. After treatment with the second portion ofresin, the product is recovered and found to contain 18.1 percent SiO0.20 percent Na O, and to be 2.07 normal in dimethylamine. The degree ofpolymerization of this material is approximately 30. parts by weight ofvinyl triethoxysilane are mixed with 13.65 parts by weight of the aminesilicate prepared above and 28.5 parts by weight ofa lN solution ofdimethylamine, and this mixture is made up to 1,000 parts by weight withwater.

This mixture is applied to three 1 1 inch wide strips of E" glassfabric, style 181, heat-cleaned glass. The strips are soaked in thetreating solution for approximately 3 minutes, and passed through awringer and the wet pickup measured. The tension on the rollers isadjusted to give a wet pickup of approximately 50 percent. These stripsare placed on clean towels and dried for 10 minutes at C. in anair-circulating oven. They are rinsed in water for approximately 12minutes, wrung out, placed on clean towels and dried for 10 minutes at125 C. They are then cut into four 9 inch wide panels in the warpdirection and trimmed to 10 inch along the fill direction, the edgesbeing then frayed to a depth of about three-eighths inch by pulling outlongitudinal threads.

495 Parts by weight of a polyester resin consisting of a mixture ofstyrene with a maleic anhydride-glycol polyester copolymer, called Rohm& Haas Paraplex P43, are mixed with 5 parts by weight of benzoylperoxide powder, which is dispersed in the resin by mechanicallystirring while heating the resin to 43 C. The resin-benzoyl peroxidecatalyst mixture is then maintained at 43 C. for approximately 20minutes.

While the catalyzed resin is held at 43 C., a k inch l2.5 inch l2.5 inchsteam cover plate is placed on a hot plate maintained at the sametemperature, and covered with a 12.5 inchXl2.5 inch ferrotype chromiumplate. A 60 inch 30 inch strip of cellophane is located on the plate,and the laminate dye is sprayed with a release agent, which is anaerosol of zinc stearate. A A; inch l2.5 inch l2.5 inch metal plate witha Vs inch l0.5 inch 9.5 inch cutout is then placed on the dye, coveredwith the cellophane, and the glass fabric panels are laid on the dyewith each layer being treated with sufficient resin to cover and wet inthe glass fabric. Twelve pieces of fabric are used to make l2-plylaminate, and the excess resin and air bubbles are squeezed out byrolling with a rubber roller. The laminate is then covered with thefolded cellophane, a second ferroplate placed on top and the wholeassembly of dye and resin enclosed in aluminum foil.

This is placed in a hydraulic ram press preheated to 175 F. and pressedat a pressure of 7 tons per square inch, which serves to eliminate theexcess resin. It is held at 175 F. for 15 minutes and then heated to 225F. and held at this temperature for 20 minutes. It is then heated to 275F. and held at this temperature for 20 minutes. The heat is turned off,the press cooled to 240 F. with air, after which cooling water ispressed through the heaters to cool the press to 225 F. Pressure isrelieved, the laminates removed and cut into 1 inch 4.5 inch test bars,which are sanded to a thickness of 0.5 inch i002 inch.

The modulus of rupture of these bars is determined on a 2 inch span withan lnstron tester. Five bars are tested to determine the dry strengthand an additional five bars tested to determine the average wetstrength, following boiling in water for a two hour period.

The rupture strength of this laminate is 71,500 p.s.i. when dry and53,100 p.s.i. after boiling.

For comparison, a laminate prepared using the organosilane alone at anidentical level of silicon atoms on the glass cloth and adjusted to thesame total basicity using dimethylamine has a dry transverse rupturestrength of 70,600 p.s.i. and a wet strength of 63,100 p.s.i. Thus itwill be noted that the much less expensive 50:50 aminesilicate-organsilane mixture has substantially as high a strength as thepure organosilane.

EXAMPLE 2 The same procedures and materials as used in Example 1 areemployed, except that the relative proportions of the organosilane andthe amine silicate are adjusted to give 75 percent of the treatingsilicon atoms in the form of the organosilane and 25 percent in the formof the amine silicate. The dry strength of this laminate is found to be76,000 psi. and the wet strength 67,000 p.s.i. Here again it will benoted that the amine silicate may be substituted for the organosilane,and in this instance actually give a stronger laminate than is obtainedusing the organosilane alone. It is noted that glass cloth treated withthis composition and the composition of Example has a softer hand and amuch lower tendency to generate static charges in handling than theorganosilane treated control described in Example 1.

1 claim:

1. An aqueous coupling agent formulation consisting essentially of from25 to 90 percent of the total silicon present in the form of anorganofunctional silane of the general formula R,,SiX., wherein R isselected from the group consisting of carboxyalkenyl of one to 18 carbonatoms, alkyl of one to 18 carbon atoms, aminoalkyl of one to 18 carbonatoms, thioalkyl of one to 18 carbon atoms and epoxy substituted alkylof one to 18 carbon atoms; X is selected from the group consisting ofhydroxyl,

halogen, alkoxy of one to six carbon atoms, and amino; n is a positiveinteger of from one to three; and from 10 to 75 percent of the totalsilica present in the form of an amine silicate having a degree ofpolymerization less than 1,000 and the amine component being at leastone amine selected from the group consisting of (1) compounds having theformula:

wherein R,, R and R are independently selected from the group consistingof hydrogen, alkyl of one to six carbon atoms and alltanol of one to sixcarbon atoms, with the proviso that R,, R and R cannot all be hydrogensimultaneously; (ll; morpholine, and (Ill) cyclohexylarnine, the aminebeing present in an amount of at least 01 mole per mole of silica in theform of an amine silicate.

2. An aqueous coupling agent formulation of the composition of claim 1wherein 50 to percent of the total silicon are in the form of anorganofunctional silane and 10 to 50 percent are in the form of an aminesilicate.

3. An aqueous coupling agent formulation of the composition of claim 1wherein the amine silicate is dimethylamine or ethanolamine.

4. An aqueous coupling agent formulation of the composition of claim 3wherein the organofunctional silane is vinyltriethoxysilane,gamma-aminopropyltriethoxysilane orgamma-methacrylopropyltrimethoxysilane.

5. A reinforcing filler material coated with 0.01 to 20.0 percent byweight of a polymerized coupling agent formulation of the composition ofclaim 1.

2. An aqueous coupling agent formulation of the composition of claim 1wherein 50 to 90 percent of the total silicon are in the form of anorganofunctional silane and 10 to 50 percent are in the form of an aminesilicate.
 3. An aqueous coupling agent formulation of the composition ofclaim 1 wherein the amine silicate is dimethylamine or ethanolamine. 4.An aqueous coupling agent formulation of the composition of claim 3wherein the organofunctional silane is vinyltriethoxysilane,gamma-aminopropyltriethoxysilane orgamma-methacrylopropyltrimethoxysilane.
 5. A reinforcing filler materialcoated with 0.01 to 20.0 percent by weight of a polymerized couplingagent formulation of the composition of claim 1.